<?php
interface Discountable {
	/**
	 * Discount on sale program
	 *
	 * @param array $serviceArr
	 *   [service_id => service_price] 
	 *    
	 *   service_price: is the price to discount on
	 * 
	 * @return the discount amount
	 */
	function discountOnSaleProgram($serviceId, $servicePrice);
}
?>